This invention relates to a development apparatus and particularly a magnetic brush development apparatus and to an electrostatographic reproducing machine incorporating the development apparatus.
Magnetic brush development has been widely used in a variety of commercially available electrostatographic copying machines. One problem associated with many types of development systems when used to develop an image on a moving imaging surface such as the xerographic drum of a copier is the problem of maintaining alignment between the development system and the xerographic drum. In U.S. Pat. Nos. 3,721,209 to Szostak et al. and 3,671,119 to Engel et al. there are disclosed cascade development systems wherein followers on the housing ride against the drum in order to space the housing from the drum. In U.S. Pat. No. 3,011,474 to Ulrich a xerographic development electrode apparatus is provided wherein the electrode is spaced from a drum-like imaging member by means of followers which ride on the drum surface. In U.S. patent application Ser. No. 255,259, filed May 22, 1972 now U.S. Pat. No. 3,854,449, by Davidson and assigned to the assignee of the instant invention there is disclosed a magnetic brush development system wherein the development roll is spaced from the drum by means of a follower roll which is coupled to the developer housing and rides against the drum. In each of these apparatuses close alignment is maintained with the drum surface by means of followers.
The above-noted approaches, however, do not take into account skew between the imaging surface and the development member and also drum run-out phase variations, which are, for example, variations in the out of roundness of a drum along its axial length. Run-out at one end of a drum can be out of rotational phase with the run-out at the other end.
In U.S. Pat. No. 3,628,504 to Richmond, a mounting apparatus for a development apparatus of an electrostatic copier enables the spacing between the magnetic brush developer and the xerographically sensitive element to be varied across the width of the brush. The apparatus included two independently adjustable eccentric cams which bear upon the developer housing to set the spacing between the housing and the xerographically sensitive element. The spacing is maintained constant independent of dimensional changes in the copier frame units by a spring loaded member bearing on the developer housing. The teachings of this patent describe an approach which could be utilized to overcome skew between a magnetic brush roll and the surface of the imaging member.